Hydraulic counterbalance for drill pipes



March 29, 1938. J. c. STOKES 2,112,254

HYDRAULIC COUNTERBALANCE FOR DRILL PIPES Filed April 21, 1936 JTC. STOKES.

@Mm @QQQ J gunners- Patented Mar. 29, 1938 UNITED STATES PATENT OFFICE HYDRAULIC COUNCIlZE R-BALANCE FOR DRILL IPES 4 Claims.

The invention relates to a means and method of supporting all or part of the weight of a drill stem in a well bore which is being drilled by the rotary method.

As the art of drilling wells by the rotary method has progressed, the wells have become deeper and deeper. It will be understood that by the rotary method a drill bit is connected to the end of a piece of drill pipe and is caused to be rotated in order to penetrate the earth. As the drill bit advances, section after section of pipe is added to the drill stem. Mud is circulated down through the drill stem and up through the well bore to carry away the cuttings from the drill bit, to maintain the wall of the well bore and to overcome formation pressures encountered.

As the wells are drilled deeper and deeper, the stresses and strains on not only the drill pipe but the derrick, hoisting cables, drawworks and rotary, increase many fold. The usual type of larger size drill pipe now in general use for the deeper wells has a weight of about 25 pounds per foot. Each section of pipe is connected to the next section by a tool joint having a weight of about 1'75 pounds. It is apparent from the foregoing that the average weight of pipe and tool joints per foot is about 30 pounds. Thus, if the well has beendrilled to 10,000 feet, the weight of the string of large size drill pipe alone would approximate 300,000 pounds, one-sixth of which would be deducted for the flotation effect of the pipe in the drilling mud, leaving approximately 250,000 pounds to be suspended in the well bore.

This tremendous weight must be suspended from the derrick by the crown block and cables while it is being rotated at from 50 to 2-00 revolutions per minute to perform the drilling operation.

It seems obvious from the foregoing that the maximum stresses on the pipe itself may be exceeded in event the length of the pipe is increased. Instances have occurred where the pipe has broken in two because of the strain of its own weight when it was subjected to torsional stresses.

The present invention directs itself to an arrangement whereby a portion of the weight of the drill pipe can be supported at any desired elevation so as to relieve the strain upon the upper portions of the pipe of the stem.

Another object of the invention is to provide a supporting construction intermediate the ends of a drill stem so as to support a portlqn Qi the 55 weight thereof.

Another object of the invention is to provide a method of suspending part of the weight of the drill stem at any desired elevation in the well bore.

Another object of the invention is to provide 5 a method wherein the weight which is to be applied to the drill bit for the drilling operation is determined by the weight of a length of pipe directly above the bit and wherein a portion of the balance of the weight of the drill stem 10 may be supported by hydraulic pressure.

Another object of the invention is to support a portion of the weight of the drill pipe in the well bore by hydraulic pressure.

Still another object of the invention is to 15 provide a rotatable piston for supporting drill pipe in the well bore.

Still another object of the invention is to provide a hydrostatic counterbalance for thedrill pipe in deep wells.

A still further object of the invention is to reduce the strain on a string of drill pipe which is caused by the weight of the drill pipe itself by supporting some of the drill pipe by a hydrostatic pressure in the well bore.

Still another object of the invention is to control the movement of the drill pipe in the well bore by controlling hydraulic pressure which tends to support a portion of the weight of the drill pipe.

Still another object of the invention is to recover a drill pipe or to remove a stuck pipe 1 from the well bore by applying hydraulic pressure thereto.

Still another object of the invention is to 35 provide in combination with a drill pipe in a Well bore, a casing and piston arrangement so that hydraulic pressure applied beneath the piston will tend to support a part of the weight of the drill stem.

Other and further objects of the invention will be readily apparent when the following description is considered in connection with the accompanying drawing, wherein:

Fig. 1 is a side elevation of the arrangement showing certain of the parts in section to illustrate the general construction thereof.

Fig. 2 is an enlarged view of the support construction as it is located in the well bore.

Fig. 3 is a diagrammatic view showing a simple form of the invention.

In Fig. l the earth formation is indicated generally at 2 and has been drilled to form a well bore 3. This bore may or may not have been fitted with a casing 4 in order to support the formation. In Fig. l the casing 4 has been fitted and the lower end has been fixed in position with a body of cement as at 5. This casing 4 is generally known as a surface casing and extends into the earth a suflicient distance to form an anchor for the casing-head 6 to which the various well head fittings are attached.

In the present instance a string of casing I has been run into position in the surface casing 4 and may extend down into the well for any desired distance. This pipe is sealed to the casinghead by the threaded connection 9. During the drilling operation a drill stem I0 is lowered into the well bore with the bit H attached to the lower end thereof, and in the usual rotary method of drilling, this drill stem I0 is rotated to perform the cutting operation and a stream of flushing fluid or drilling mud is pumped downwardly through the drill stem and out through the ports l3 in the drill bit. This mud will then flow upwardly through the well bore at I4 and through the surface casing 4 so that it may discharge through the return pipe IS. The construction so far described may be that usually employed in the drilling of an oil well, the circulation of mud also serving to maintain the walls of the well bore 14.

When the Well has been drilled to a considerable depth-the weight of the drill pipe becomes excessive and in accordance with the present invention it is desirable to support some of the weight of the drill stem in the well bore by hydrostatic pressure, rather than attempting to suspend the entire load from the crown block on the derrick. Any desired amount of the weight may be taken up in the well bore by applying a supporting pressure so long as the drill stem does not buckle above the point of application of the weight. The guides 48 may be placed on the casing 1 if desired to center it and prevent buckling.

In order to apply hydrostatic pressure to the drill stem to support the weight thereof, a piston head 20 has been inserted between any two adjacent sections of the drill pipe. This piston head is best seen in Fig. 2 and includes a coupling 2| which is fixed to the lower section of drill pipe 22. This coupling 2| has fixed thereto a spindle 23 which is enlarged at 24 to provide a shoulder 25 for an anti-friction bearing 26. A second or duplicate anti-friction bearing 21 may be provided if desired in order that the enormous weight may be rotatably supported. In order that the pressure may be applied equally to the bearings 26 and 21, equalizing pads or rings 34 are placed above each bearing so that excessive pressure will compress the pad and shift part of the load to the other bearing. A sealing assembly 28 is arranged on the spindle 23 and includes the supporting members 29 and the packing rings 30, which may be arranged on the inside to seal around the spindle and outside to seal with the well bore or casing I. This assembly is held in position by the support collar 3| and the bolts 32. When this piston is lowered into the casing 1 it will form a substantial seal therewith, as best seen in Fig. 2, so that fluid pressure applied in the chamber 33 below the piston will serve to support the piston and a variable weight applied thereto depending on the differential piston area available and the fluid pressure applied.

It is intended that this piston or support member 20 can be located at any desired position in the string of drill pipe depending upon the various conditions to be encountered. If little or no weight is to be placed on the drill stem, then the piston can be located closely adjacent the drill bit and any pressure applied to it will support any desired amount of the Weight of the drill stem, depending upon the pressure applied. It seems obvious that under various conditions the piston or support assembly can be located at any desired elevation. If the casing I present in the well is only a short casing, then the piston can be located so that it will remain in the casing and by applying the desired pressure any proportionate amount of the weight of the drill stern can be supported thereby.

It will be understood that pump pressure is applied to the top of the drill stem l 0 by suitable circulating pumps. The suction line 35 which is disposed in the tank or pit 36 serves as a source for the mud or circulating liquids. These mud pumps are capable of maintaining very high pressures so that the mud is forced out through the ports of the bit and moves upwardly through the well bore under considerable pressure. The

discharge line I5 is here shown as provided with a control valve 37 and a pressure gauge 38 before it discharges into the pit 36. By adjusting the valve 31 any desired back pressure may be applied to the well bore and, of course, this back pressure will be applied to the lower side 40 of the piston assembly 20. The differential pressure on the lower side of the piston will be available to support any weight which resists upward movement of the piston as result of this pressure application.

If desired, the casing 1 above the piston assembly 20 such as the chamber 45, may or may not be filled with liquid, depending upon the weight which is to be supported by the piston. If a considerable weight is to be carried by the piston, the casing 7 may be empty so that there would be no static head of liquid or any pressure applied to the upper surface 46 of the piston. Under these conditions the weight to be supported could be supported by the differential static head of liquid in the chamber 41 between the casings l and 4, so that if this pressure were suificient then no restriction on the discharge line l5 would be needed because the static head would be available to support a portion of the weight of the drill pipe. In event a greater weight was to be supported, however, the valve 31 could be partially closed to increase the pressure in the well bore, and in this manner could support a greater weight of the drill pipe.

A very fine adjustment of the weight to be supported by the piston 20 could be obtained either by adjustment of the valve 31 or by positioning any desired weight of liquid in the chamber 45 above the piston 20. In View of the great flexibility to be obtained in the supporting of the weight, it seems obvious that any set of circumstances might be successfully encountered with a device such as here described.

A flow line is shown as connected above the casing head 6 to the casing l for releasing of liquid from the pit 36 into the casing 7.

In event it was desired to use a hydrostatic or hydraulic pressure to assist in moving the piston 20 upwardly or supporting any portion of the weight of the drill pipe, a pressure line is shown as connected at 56 to the discharge line I5 and a control valve 51 is positioned in this line.

In this construction if it is desired to raise the drill pipe the pump pressure can be applied to this link? 5 and in this manner an enormous 5 n i lt tii in umans,

pressure can be applied to the under side of the piston 20 to raise it in the casing I. This operation might be desirable in the event the drill pipe became stuck or broken off above the piston 20, or in event some of the hoisting machinery became inoperative. It might also be utilized by employing additional pumps if for some reason an enormous pressure were to be supported by the piston. To prevent an upward flow through the drill pipe, any usual type of back pressure valve could be inserted in the drill pipe.

In event a well bore larger than the casing l were to be drilled, a collapsible or expanding bit might be used.

The present method is of advantage because if the pressure of the static head is used then there will be no increase in pressure on the formation and possibly a lesser pressure than with the regular drilling practice.

It is to be understood that the casing I may be of any desired length or size and may be lowered to follow the drilling operation and may be reduced in size in accordance with the size of the hole or bit.

Fig. 3 shows a simple form of the invention wherein all of the parts are substantially the same as are shown in the previous form except that the inside casing I of Fig. 1 has been dispensed with and the piston 60 is mounted directly in the casing 4. With this arrangement, therefore, the returns from the ports l3 in the bit will move upwardly in the well bore and a discharge pipe BI is provided which is connected to the casing 4 below the elevation of the piston 60 and this return discharges into the pit 36 the same as previously described. As seen in Fig. 3, there is no liquid in the chamber 62 which is above the piston and inside of the casing 4, so that there will be a normal difierential static pressure available on the piston to raise the same and support part of the weight of the drill stem, which pressure is equal to the difference in the weight of the liquid in the column 63 outside of the drill stem and below the piston and the column of liquid 64 which is inside of the drill stem and extends to the surface of the ground. Thus there will be aunit area differential pressure which will be applied over the entire surface 65 of the piston which will tend to raise the drill stem.

Broadly the invention contemplates counterbalancing the weight of the drill pipe by hydrostatic pressure or effectingany desired manipulation of the drill pipe by applying pressure thereto.

What is claimed is:

1. In a well bore the combination of a casing a drill string therein, means on said stem to form a substantial seal with said casing, a cham ber thus formed in the casing above said seal, and a column of liquid in the well bore outside said casing whereby the pressure of the static head of liquid in the well bore outside said casing and above said seal will be available to support a portion of the weight of said drill string, and means to add liquid in said chamber to vary the available pressure on said first means.

2. A well drilling assembly to support part of the weight of the drill string in the well bore which comprises, a surface casing, a well casing sealed therein, a drill string in said well casing, a closure means around said stem in said well casing at a substantial distance from the stem in said well casing, means on said stem at a substantial distance from the top of the well to form a substantial seal with said well casing and form a chamber between the drill stem and well casing above said seal, a circulation of liquid down said drill stem and upwardly through the well bore between said casings and. against said sealing means, and means for controlling fluid pressure in said chamber whereby inward pressure tending to collapse the well casing is partially balanced.

4. In the art of rotary drilling of wells, the method of supporting a long drilling string in the well, which consists of supporting. that fraction of the weight of the drilling string on the bit that will effect suitable conditions for rotary drilling, supporting a substantial fraction of the weight of tfffirilling string at a point between the bottom and the top of the well and at a substantial fraction of the depth of the well from either the top or bottom thereof and supporting the remainder of the weight of the drilliii'g'stririg" at a point above the top of the well.

JOHN C. STOKES. 

